Søren Kierkegaard’s Concluding Unscientific Postscript (1846) is an inquiry into the subjectivity of truth, and into the truth of subjectivity. Kierkegaard explains how objective truth may differ from subjective truth, and how objectivity differs from subjectivity. Kierhkegaard describes how objective truth may be an outer truth, and how subjective truth may be an inner truth. Kierkegaard distinguishes between speculative philosophy as a mode of reasoning which seeks objective truth, and religious faith as a mode of being which seeks subjective truth.

According to Kierkegaard, the objective thinker is interested in objective truth, while the subjective thinker is interested in subjective truth. Objective truth includes historical truth and philosophical truth. Subjective truth includes religious truth. The objective thinker is indifferent to the truth of subjectivity, while the subjective thinker finds an eternal happiness in subjectivity. For the subjective thinker, eternal happiness is an absolute good which is attained by faith. Faith is a passionate inwardness which affirms the truth of subjectivity.

For Kierkegaard, objective truth is characterized by outwardness, while subjective truth is characterized by inwardness. The objective thinker does not find an eternal happiness in subjective truth, and is disinterested in the truth of subjectivity. The objective thinker is interested in what defines existence, while the subjective thinker is interested in how existence is defined.

Reflection on the nature of existence may be objective or subjective. Truth may be reflected upon objectively or subjectively. Kierkegaard argues that the objective thinker finds truth by approximation, while the subjective thinker finds truth by appropriation. The objective thinker has a need to quantify certainty or probability, while the subjective thinker ultimately must accept uncertainty. According to Kierkegaard, faith cannot be attained by approximation, or by an effort to quantify deliberation into a higher degree of certainty. Faith can only be attained by an appropriation or acceptance of the condition of uncertainty. Thus, faith requires a leap from disbelief to belief. Faith is a state of objective uncertainty in which the individual affirms his or her own subjectivity.

According to Kierkegaard, faith is a subjective, personal, passionate interestedness in attaining eternal happiness, as found through appropriation. Faith is a category of decision-making in which an individual confronts an “either-or” situation, either accepting or rejecting subjectivity. Kierkegaard argues that the falsehood of objectivity may be revealed by a lack of need for personal commitment, and by a lack of need for decision-making, while the truth of subjectivity may be revealed by a need for personal commitment, and by a need for decision-making. The speculative thinker attempts to stand apart from his or her own existence, and attempts to view existence objectively. In contrast, the subjective thinker realizes that he or or she cannot stand apart from existence, and that the truth of his or her own existence is found in his or her own subjectivity.

Kierkegaard explains that truth is a paradox, in that it is objectively defined as subjectivity, and in that the outwardness of objectivity is also the inwardness of subjectivity. Truth may be objectively defined as a passionate inwardness, which may change in depth or intensity according to the experience of the subjective thinker. Inwardness is an ethical infinity in which the individual may find eternal happiness.

Although truth may be appropriated by faith, faith must be surrendered in order to be objective. Thus, Kierkegaard admits that truth may be defined from either an objective or subjective point of view. Kierkegaard does not deny that speculative thinking may be useful to explain matters about which it is not necessary to have faith. However, questions about matters of faith (or questions about whether to have faith) must be answered subjectively.

Kierkegaard argues that to know the truth of personal existence is to be aware of uncertainty. Truth is not an abstract set of relations, or an immutable state of being. Truth is found in the existence of the subjective thinker, and is more passionately appropriated as the subjective thinker progresses from the aesthetic to the ethical to the religious stages of existence. The subjective thinker is always in a state of becoming. The passion of the subjective thinker may be revealed by a deepening inwardness, and by a heightening of subjectivity. Being is a process of becoming, and is thus a state of uncertainty.

According to Kierkegaard, the objective point of view regarding the nature of truth is taken by speculative philosophy, while the subjective point of view regarding the nature of truth is taken by religious faith. Kierkegaard describes Hegel’s philosophy as representing a speculative mode of thinking. While Hegel describes truth as a continuous world-historical process, and as the becoming of an absolute reality, Kierkegaard describes truth as a leap of faith, and as the becoming of the individual’s subjectivity. While speculative thinking reflects on concrete things abstractly, subjective thinking reflects on abstract things concretely.

Kierkegaard admits that subjectivity becomes comical when it is misplaced; i.e. when subjectivity is misinterpreted as objectivity. The subjective thinker may become either comical or tragic when he or she tries to achieve an objective certainty (or the highest possible degree of probability) concerning an aspect of truth which can only be known by faith. The subjective thinker may become either comical or tragic when he or she tries to achieve an objective certainty by means of faith, which is defined by objective uncertainty. The subjective thinker may also become comical or tragic when he or she falsely pretends to be infinitely interested in attaining eternal happiness.

Kierkegaard defines three stages of existence: 1) the aesthetic, 2) the ethical, and 3) the religious. The aesthetic stage is a stage in which the individual is interested in pleasure and enjoyment The aesthetic stage is not characterized by the passionate engagement and personal commitment which are characteristic of the higher stages of existence. The ethical stage is a higher stage of personal commitment, and the religious stage is the highest stage of personal commitment. Inwardness includes the ethical, ethical-religious, and religious stages of existence.

Kierkegaard argues that the religious stage is the highest stage of subjectivity. The religious person understands that suffering is inherent to the religious experience. While the aesthete considers suffering to be something accidental, the religious person understands that suffering is an essential aspect of his or her own existence. This is the paradox of faith, that in the process of attaining eternal happiness, the subjective individual is able to understand the meaning of suffering. In the process of discovering subjective truth, the individual becomes more aware of his or her own objective uncertainty.